Clostridium botulinum

Categorization

Cell Wall: Gram Positive

Shape: Spore-forming Rod

Metabolism: Obligate Anaerobe

Transmission

Overview

The causes of botulism tend to be slightly different in adults and infants.

Adult Botulism

C. botulinum spores may contaminate meats and vegetables that undergo packaging in cans. Within the anaeorbic environment of the can the spores can germinate, grow, and elaborate the Botulinum Exotoxin. Thus disease in adults is caused by ingestion of the pre-formed botulinum exotoxin while the actual bacteria may be dead.

Infant Boutlism

Food contaminated with C. botulinum spores, especially honey products, is ingested by infants. The spores germinate inside the infant's GI system, grow, and elaborate botulinum exotoxin. Thus disease in infants is caused by growing bacteria within the GI system which are actively elaborating exotoxin.

Virulence Factors

Botulinum Exotoxin:

Botulinum exotoxin is a neurotoxin which irreversibly blocks release of acetylcholine (Ach) from peripheral nerves at the synapse. The ingested toxin is absorbed and enters the blood which delivers it to peripheral nerve synapses. The gene for the botulinum exotoxin is carried on a lysogenic phage and is thus transmitted by transduction.

Clinical Consequences

Adult Botulism

Characterized by a descending paralysis which begins with diplopia and dysphagia. Paralysis continues with general muscle weakness ultimately resulting in respiratory depression and death. Importantly, this paralysis is characterized by flaccidity, rather than the rigor associated with C. tetani.

Infant Botulism

Infants first develop constipation followed by dysphagia and a generalized muscle weakness.

Treatment

Adult botulism: Antitoxin, an antibody which binds the botulinum toxin